Isomerization of 5-vinylbicyclo{8 2.2.1{9 hept-2-enes

ABSTRACT

5-Vinylbicyclo(2.2.1)hept-2-enes heated in the presence of a titanium catalyst system are isomerized to 5ethylidenebicyclo(2.2.1)hept-2-enes. The catalyst system of this invention comprises a titanium compound, a Group IA, IIA or IIIA metal and an aluminum halide. The catalyst system is highly efficient and capable of rapidly isomerizing 5vinylbicyclo(2.2.1)hept-2-enes. 5-Ethylidenebicyclo(2.2.1)hept-2enes are useful comonomers for polymerization with Alpha olefins such as ethylene and propylene.

United States Patent Schneider l4 1*Sept. 26, 1972 [54] ISOMERIZATION OF 5- 3,535,395 10/ 1970 Schneider ..260/666 PY VINYLBICYCLO[2.2.lgZHEPT-Z-ENES 3,535,396 10/ 1970 Schneider ..260/666 PY vInventor: fg g S i Brecksvme, Schne1der Ohio 3,565,961 2/1971 Nagase et a1. ..260/666 PY 3,594,433 7/1971 Schn ider ..260/666 FY [73] Assignee: The B. F. Goodrich Company, New e York Primary Examiner-Herbert Levine l Notice: The portion of the term of this Assistant Examiner-Veronica O'Keefe patent subsequent to July 20, 1988, Attorney-J. Hughes Powell, Jr. et al. has been disclaimed. 22 Filed: June 14, 1971 [57] ABSTRACT [211 App] No 153 098 5-Viny1bicyc1o[2.2.1]hept-2-enes heated in the presence of a titanium catalyst system are isomerized to 5-ethylidenebicyclo[2.2. 1 lhept-Z-enes. The catalyst U-S. CL system of this invention comprises a titanium com- [51] Int. Cl ..C07C 5/28 pound, a Group IA A or metal and an [58] Fleld of Search ..260/666 PY mil-mm halide. The catalyst system is highly efficient and capable of rapidly isomerizing S-vinyl- [561 References bicyclo[2.2.1]hept-2-enes. 5-Ethy1idenebicyclo[2.2.l UNITED STATES PATENTS ]hept-2enes are useful comonomers for polymerization with a-olefins such as ethylene and propylene. 3,151,173 9/1964 Nyce ..260/666 PY 3,347,944 10/1967 Fritz et al. ...........260/666 PY 6 Claims, No Drawings BACKGROUND OF THE INVENTION Previously known catalysts for the isomerization of -vinylbicyclo[2.2.1]hept-2-ene to S-ethylidenebicyclo[2.2.llhept-Z-ene have not been completely satisfactory. Large amounts of catalyst are often necessary to achieve acceptable rates of isomerization. Significant amounts of by-products and poor catalyst efficiency were often noted.

SUMMARY OF THE INVENTION I have now found quite unexpectedly an improved catalytic process for the isomerization of S-vinylbicyclo[2.2.1]hept-2-enes to 5-ethylidenebicyclo[2.2 .llhept-Z-enes wherein high catalyst efficiencies are achieved. Rapid isomerization rates are realized with the process of the present invention. The increased rate of isomerization and excellent catalyst efficiencies obtained with the presentcatalysts are significant since it is now possible to achieve isomerization in very short periods of time employing very low catalyst concentrations. In this manner by-products formed during the isomerization are minimized and in most instances completely eliminated. The present process utilizes a titanium catalyst comprising a titanium' tetravalent compound, a Group I, II or III metal and an aluminum halide.

DETAILED DESCRIPTION The isomerization reaction of this invention may be represented as follows:

wherein R is a hydrogen or an alkyl group containing from 1 to 4 carbon atoms. The present process is particularly advantageous for the isomerization of S-vinylbicyclo[2.2.l]hept-2-ene (where R=H) since this material is readily available from the Diels-Alder addition of 1,3-cyclopentadiene and 1,3-butadiene. Other 5-vinylbicyclo[2.2.l]hept-2-enes, such as methyl-5- vinylbicyclo[2.2.llhept-Z-enes obtained from the reaction of 1,3-cyclopentadiene with piperylene or methyl 1,3-cyclopentadiene and butadien'e, are just as effectively isomerized by the present process.

While any titanium compound may be used, the particular titanium compounds employed were dicyclopentadienyl titanium dihalide; and titanium tetrahalides and titanium alcoholates which correspond to the structural formula wherein X is chlorine, bromine or iodine, R is a hydrocarbon radical containing from one to 12 carbon atoms and more preferably one to eight carbon atoms, such as alkyl, cycloalkyl, aryl and alkaryl groups, and y is an integer from 0 to 4. Excellent results are obtained with dicyclopentadienyl. titanium chloride, titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, C2H5OTiCl (C2H50)2TiCl2, (C2H5O)3 TiCl, tetraethyl titanate, tetra-(iso-propyl)titanate, tetra-n-butyl titanate, tetra-(2-ethylhexyl)titanate and tetraphenyl titanate. Mixtures of these titanium compounds may also be employed. For example, mixtures of titanium tetrahalides with tetraalkyl titanates are useful as the titanium component in forming the catalyst of the present process.

Any of the available alkali or alkaline earth metals and aluminum may be used in the process but sodium, because of availability and cost, is preferred. Useful are lithium, potassium, calcium, magnesium and the like. To be used most effectively, the sodium should be in finely divided or activated form as in the form of sodium sand, dispersions of sodium in inert solvents as mineral oil, or the isomerization reaction conducted at temperatures above 975C, which isthe melting point of sodium, liquid sodium being particularly effective. Activated sodium is well known in organic syntheses.

While any aluminum halide may be used, better results are obtained with aluminum chloride and aluminum bromide.

The present catalyst systems are obtained by contacting the titanium compound with the metal and an aluminum halide. The catalyst may be prepared prior to use or the individual catalyst components may be mixed in the reactor in the presence of the 5-vinylbicyclo[2.2.l]hept-2-ene. If the catalyst system is prepared prior to the isomerization the components are generally admixed in an inert solvent. This latter method facilitates subsequent storage, handling and charging of the catalyst and is a useful means to control the reaction exotherm.

While large amounts of the titanium compound may be employed, it is an advantage of this invention that small amounts in the range from about millimols per mol 5-vinylbicyclo[2.2.llhept-Z-ene to about 0.1 millimol per mol 5-vinylbicyclo[2.2.1lhept-2-ene may be used. More of the titanium compounds per mol of 5- vinylbicyclo[2.2.1]hept-2-ene can be employed if.

minum chloride to titanium compound and about 2:1 mols of sodium per mol of titanium compound. While a molar excess of these constituents may be used, there is no particular advantage in such excess.

The isomerization is carried out by reacting the vinylbicyclo[2.2.1]hept-2-ene in the presence of the titanium catalyst system. The 5-vinylbicylo[2.2.1]hept 2-ene is generally charged to the reactor and the preformed catalyst or the individual catalyst components added thereto. The catalyst or individual catalyst components may be completely charged at the outset of the isomerization or charged continuously as the isomerization progresses. The process may be conducted employing either batch or continuous techniques. Prior to the introduction of the pre-formed catalyst or the titanium compound if the catalyst is to be prepared in situ, an amount of organometallic compound may be charged to the reactor to remove small amounts of undesirable impurities present in the system. The S-ethylidenebicyclo[2.2.1]hept-2-enes can be recovered by fractional distillation or it may be removed continuously throughout the run if continuous operation is employed.

While it is not necessary and bulk reactions are satisfactory, the isomerization may be conducted in an inert diluent such as the aromatic or saturated aliphatic hydrocarbons. Higher boiling saturated hydrocarbons may be employed since they do not interfere with the recovery of the 5-ethylidenebicyclo[2.2.l]hept-2-ene and also permit operation of the process within the desired temperature range without the use of pressure vessels. Useful hydrocarbon solvents include pentane, isopentane, 2,2-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, n-hexane, isohexane, 3methylhexane, n-heptane, n-octane, isooctane, cyclohexane, benzene, toluene, the xylenes, mesitylene and the like or mixtures thereof. If a diluent is employed the ratio of the diluent to 5-vinylbicyclo[2.2.1]hept-2-ene will generally range between about 1:10 and about 1021.

It is not essential that the 5-viny1bicyclo[2.2.1]hept- 2-ene be absolutely pure, however, the presence of large amounts of impurities should be avoided for best results. Small amounts of impurities such as water, alcohols, peroxides and air present in the S-vinylbicyclo[2.2.1]hept-2-ene or diluent can be tolerated, however, it is preferred they be removed by the addition of a scavenging agent, which in this case can also serve as the modifier, or by some other suitable means. Distillation or sieving of the 5-vinylbicyclo[2.2.1]hept- 2-ene and diluent prior to use will generally suffice to remove most impurities which seriously impair the catalyst efficiency or promote formation of polymeric materials. It is often advantageous to employ sufficient excess of the alkali metal so that it willalso serve as a scavenger to remove impurities such as oxygen, alcohols, water and the like present in the system.

The isomerization process is conducted under a dry atmosphere of an inert gas such as nitrogen or argon and may be conducted at atmospheric, sub-atmospheric or super-atmospheric pressure depending on the reaction conditions and diluent employed.

The isomerization process is conducted at temperatures of about 25C., up to 300C. or above. Excellent results, i.e., high catalyst efficiency and a rapid isomerization have been obtained within the temperature range of about 25 to 200C. The increased rate of isomerization achieved with the present invention permits the isomerization of 5-vinylbicyclo[2.2.1]hept-Z- ene to 5-ethylidenebicylco[2.2.l]hept-2-ene on a continuous basis. At room temperature the rate of isomerization, although considerably slower than obtained at elevated temperatures, is nevertheless significant and a reasonable degree of conversion can be achieved.

The invention is illustrated more fully as follows by a representative example that is not intended to limit the scope thereof.

0.2 M01 (25 ml) 5-vinylbicyclo[2.2.l]hept-2-ene prepared by the Diels-Alder reaction of 1,3-cyclopentadiene and 1,3-butadiene as described by A.F. Plate and NA. Belikova in ZHURNAL OBSHCHEI KHlMll, 30, No. 12, 3945-54 (1960) was charged to a dry argon-purged reactor containing an equivalent amount of mesitylene, 0.133 gram of AlCl 20 millimols of sodium in a 50 percent suspension in mineral oil and 1 gram dicyclopentadienyl titanium chloride (4 millimols) were added at room temperature with stirring while maintaining the argon purge. The reactor and its contents were kept at room temperature for a week. The resulting reaction product analyzed by vapor phase chromatography was found to contain 88 percent 5- ethylidenebicyclo[ 2.2. 1 ]hept-2-ene.

in a series of similar examples, 12.5 grams, 0.1 mol, of 5-vinylbicyclo[2.2.1]hept-2-ene, 12.5 grams of mesitylene, 2 millimols of titanium compound, 11 millimols of sodium in 50 percent suspension in mineral oil, and 3.5 millimols of AlCl were charged to sealed reactors. With tetrabutyl titanate, at C. after 72 hours, 91 percent 5-ethylidenebicyclo[2.2.l]hept-2- ene was obtained. With tetra-2-ethylhexyl titanate, at C. for 48 hours 78 percent S-ethylidenebicyclo[2.2. l ]hept-2-ene was obtained.

Copolymers of ethylene, propylene and S-ethylidenebicyclo[2.2.]]hept-Z-ene are readily prepared by methods known to those skilled in the art. Such elastomers are useful in the manufacture of tire carcasses and sidewalls.

I claim:

1. A process for the isomerization of 5-vinylbicyclo[2.2. l ]hept-Z-enes to 5-ethylidenebicyclo[ 2.2 .1]hept-2-enes which comprises contacting a 5-vinylbicyclo[2.2.11hept-2-ene of the formula wherein R is a hydrogen or an alkyl group containing from 1 to 4 carbon atoms with a catalyst formed by mixing (1) a titanium compound of the formula wherein X is chlorine, bromine or iodine, R is a hydrocarbon radical containing from one to 12 carbon atoms, and y is an integer from 0 to 4, or mixture thereof, (2) a Group IA, "A or IllA metal, and (3) an aluminum halide.

6 2. The process of claim 1 wherein the isomerization titanate, (2) is sodium and 3) is AlCl is conducted at a temperature between about 25 C. 5. The process of claim 4 with about 100 millimols to and 300 C. with about 2 to mol equivalents of (2) 0 1 rpjllirnol 7 0f 1) per mol S-vinylbicyclo[2.2.1] and about 1 to 5 mol equivalents of (3) per mol h P -Z- ne H V w equivalent of l 5 6. The process of claim 5 wherein about 50 millimols I 3. The process of claim 2 wherein the 5-vinylt0 1 millimol (1) per mol 5-vinylbicyclo [2.2.1]heptbicyclo[2.2.1]-hept2-ene is 5-vinylbicyclo[2.2. l ]heptis P y 2-ene.

4. The process of claim 3 wherein (1) is a tetraalkyl 

2. The process of claim 1 wherein the isomerization is conducted at a temperature between about 25* C. and 300* C. with about 2 to 10 mol equivalents of (2) and about 1 to 5 mol equivalents of (3) per mol equivalent of (1).
 3. The process of claim 2 wherein the 5-vinylbicyclo(2.2.1)-hept-2-ene is 5-vinylbicyclo(2.2.1)hept-2-ene.
 4. The process of claim 3 wherein (1) is dicyclopentadienyl titanium dihalide, (2) is sodium and (3) is AlCl3.
 5. The process of claim 3 wherein (1) is a tetraalkyl titanate, (2) is sodium and (3) is AlCl3.
 6. The process of claim 4 with about 20 millimols to 0.001 millimol of (1) per mol 5-vinylbicyclo(2.2.1)hept-2-ene.
 7. The process of claim 6 wherein about 5 millimols to 0.01 millimol (1) per mol 5-vinylbicyclo(2.2.1)hept-2-ene is employed. 